# The visitor that determine flowcontext for nodes
private class FlowVisitor
	super Visitor

	var current_flow_context = new FlowContext

	var toolcontext: ToolContext

	init
	do
		flows.add(current_flow_context)
		current_flow_context.is_start = true
	end

	var first: nullable ANode = null

	redef fun visit(node)
	do
		if first == null then first = node

		if current_flow_context.node == null then current_flow_context.node = node
		node.accept_flow_visitor(self)
		if node isa AExpr then
			var flow = self.current_flow_context
			node.after_flow_context = flow
			# Force the creation of a specific merge after the analysis of the node.
			if flow.when_true != flow or flow.when_false != flow then
				self.make_sub_flow
				self.current_flow_context.name = "AUTOSUB"
			end
		end

		if first == node then
			#self.printflow
		end
	end

	fun visit_expr(node: AExpr): FlowContext
	do
		self.enter_visit(node)
		return node.after_flow_context.as(not null)
	end

	var flows = new Array[FlowContext]

	fun printflow
	do
		var file = new FileWriter.open("flow.dot")
		file.write("digraph \{\nnode[shape=box];")
		for f in flows do
			var s = ""
			if f.node isa AExpr then
				s = "\\nmain={f.node.as(AExpr).after_flow_context.object_id}"
			end
			file.write "F{f.object_id} [label=\"{f.object_id}\\n{f.node.location}\\n{f.node.class_name}\\n{f.name}{s}\"];\n"
			for p in f.previous do
				s = ""
				if f.when_true == p then s = "[label=TRUE, style=dotted]"
				if f.when_false == p then s = "[label=FALSE, style=dotted]"
				if f.when_true == p and f.when_false == p then s = "[label=TRUE_FALSE, style=dotted]"
				file.write "F{p.object_id} -> F{f.object_id}{s};\n"
			end
			for p in f.loops do
				file.write "F{p.object_id} -> F{f.object_id}[label=LOOP, style=dashed, constraint=false];\n"
			end
		end
		file.write("\}\n")
		file.close
	end


	fun make_sub_flow: FlowContext
	do
		var flow = new FlowContext
		flows.add(flow)
		flow.node = current_node
		flow.add_previous(self.current_flow_context)
		self.current_flow_context = flow
		return flow
	end

	fun make_merge_flow(flow1, flow2: FlowContext): FlowContext
	do
		var flow = new FlowContext
		flows.add(flow)
		flow.node = current_node
		flow.add_previous(flow1)
		flow.add_previous(flow2)
		self.current_flow_context = flow
		return flow
	end

	fun make_true_false_flow(true_flow, false_flow: FlowContext): FlowContext
	do
		var flow = new FlowContext
		flows.add(flow)
		flow.node = current_node
		flow.add_previous(true_flow)
		flow.add_previous(false_flow)
		flow.when_true = true_flow
		flow.when_false = false_flow
		self.current_flow_context = flow
		return flow
	end

	fun make_sub_true_false_flow: FlowContext
	do
		var orig_flow = self.current_flow_context
		var true_flow = new FlowContext
		flows.add(true_flow)
		true_flow.node = current_node
		true_flow.add_previous(orig_flow)
		true_flow.name = "TRUE"
		var false_flow = new FlowContext
		flows.add(false_flow)
		false_flow.node = current_node
		false_flow.add_previous(orig_flow)
		false_flow.name = "FALSE"
		return make_true_false_flow(true_flow, false_flow)
	end

	fun make_unreachable_flow: FlowContext
	do
		var flow = new FlowContext
		flows.add(flow)
		flow.node = current_node
		flow.add_previous(self.current_flow_context)
		flow.is_marked_unreachable = true
		self.current_flow_context = flow
		return flow
	end

	fun merge_continues_to(before_loop: FlowContext, escapemark: nullable EscapeMark)
	do
		if escapemark == null then return
		for b in escapemark.escapes do
			var before = b.before_flow_context
			if before == null then continue # Forward error
			before_loop.add_loop(before)
		end
	end

	fun merge_breaks(escapemark: nullable EscapeMark)
	do
		if escapemark == null then return
		for b in escapemark.escapes do
			var before = b.before_flow_context
			if before == null then continue # Forward error
			self.make_merge_flow(self.current_flow_context, before)
		end
	end
end